Introduced in October last year, the Stop Online Piracy Act seeks to empower both the US Government and copyright holders with the power to shut down sites that illegally share copyrighted material.
If put into law, companies will be able to apply for a court order against any website accused of sharing content.
Possible actions that could result from an application include the blocking of online advertising, a freeze of online payment facilities, enforced blocking by ISPs and a stop to search engine results linking to the site in question.
Ad companies, ISPs or search engines who take action will be immune from prosecution.
It's all very similar to some of the proposals included in the 2010 Digital Economy Act, which evoked strong reaction in the UK as it was swiftly passed into law in the dying days Gordon Brown's Labour regime.
Critics argue that empowering companies and governments in this way is a fundamental threat to the idea of a free internet and the notion of free speech, particularly owing to its protection of those who take action against a website.
It is also feared that any sites which host user content – including the likes of YouTube, Facebook and MySpace – will be forced to tighten their rules, thus restricting internet user freedom.
Another uncomfortable aspect is that, in theory at least, a single complaint from an individual or company could lead to the blocking of a major website. The restrictions would stay in place while any investigation is carried out. Critics would prefer that sites remain available until proven of wrongdoing.
It has also been argued that the measures would do little to stop piracy. Any site forced to close would of course be free to re-open under a different name, leading to a potential never-ending spiral of cat and mouse.
While the likes of the ESA, Marvel Entertainment, Disney Publishing Worldwide, Warner Music and Viacom support SOPA, it also has a large number of high-profile opponents including Google, Facebook, Yahoo, eBay, Mozilla and LinkedIn.